I have read this entire thread and the suggestions given are heartfelt and true. Please, take them.
Take the guilt that you have and that you must "save" him and stow it away, far away. You can't save him. The very best thing for him is for you to leave.
I was given this advice and I begrudgingly took it. It saved a loved one's life.
It will either help him or not, but it's not a loving thing to do to destroy yourself for him.
Love yourself, help yourself. You have the absolute almighty power to do this, and in doing so, you will be helping your loved one.
Prayers for you and him as well...